1. Field of the Invention
The present invention relates to a vehicle door latch device.
2. Description of the Prior Art
FIG. 10 shows a lock mechanism and an opening mechanism of a conventional typical vehicle door latch device (for example U.S. Pat. No. 4,905,532). The prior art latch device comprises a lock lever A for connection to an inside lock button B, an open link C actuated by an open handle D, and a pawl lever E releasing engagement between a latch and a striker. The lock lever A in FIG. 10 is in the unlocked position, and when the open link C is moved down by the actuation of the open handle D, a pressing part F of the open link C comes into contact with a contact part G of the pawl lever E to rotate the pawl lever E, and the door is opened.
FIG. 11 shows an prior art actuator unit which moves the lock lever A to the locked position and the unlocked position. The actuator unit comprises a motor H, an output member or a worm wheel J rotated by the motor H, and an intermediate lever K rotated by the contact with the worm wheel J, and the lock lever A is connected to a rotary shaft L of the intermediate lever K. The worm wheel J returns to the neutral position when the motor H is turned off.
A first problem of the prior art device is caused by the fact that the rotational movement of the worm wheel J is transmitted to the open link C through two members, that is, the intermediate lever K and the lock lever A. If the intermediate lever K and the lock lever A can be constructed by one member, the door latch device can be simplified.
A second problem of the prior art device is caused by the fact that the lock lever A and the open link C occupy a wide range in the rear surface of a latch housing M. The lock lever A and the open link C positioned at the central portion of the rear surface make the latch device thick in the back-and-forth direction, and often causes the interference with the window glass. Furthermore, the lock lever A and the open link C positioned on the exterior side of the housing M easily receive an illegal access by using a tool which is inserted into the clearance between the window frame and the window glass of the door.
A third problem of the conventional device is caused by the fact that the lock lever A and the open link C are exposed on the outside of the housing M. The exposed lock lever A and open link C easily receive the illegal access from the outside.
Furthermore, U.S. Pat. No. 6,059,328 describes a door latch device which comprises a metal base plate (18) having a main plate (18A) in the left-and-right direction and a sub plate (18B) bent backward from the interior side portion of the main plate, a latch (3) engageable with a striker (2), a pawl lever (4) keeping engagement between the latch and the striker by being engaged with the latch, a synthetic resin striker guide (5) arranged on the rear side of the main plate and having a striker passage (17), and a metal mounting plate (21) having a rear keeping plate which comes into contact with the rear surface of the striker guide. The mounting plate (21) has a backward bent contact plate (21B) at the interior side portion thereof. An actuator (22) is fixed between the contact plate (21B) and the sub plate (18B).
A problem of this prior art device is caused by the fact that the contact plate (21B) does not so much contribute to the improvement of rigidity of the latch device. The strong external force caused by a vehicle accident or the like concentrically acts on the engaged part of the latch and the striker to move the contact plate (21B) of the mounting plate (21) toward the interior side sometimes. The moving force of the contact plate (21B) is transferred to the sub plate (18B) through the actuator, but the actuator is positioned at a lower position far from the striker passage (17), and therefore, the external force which is concentrated to the engaged part in the striker passage (17) cannot well be absorbed.
Furthermore, the striker guide (5) also has such a problem that it is large and heavy since it entirely contains the latch and the pawl lever.
Accordingly, it is an object of the present invention to provide a door latch device having an improved lock lever which functions also as an intermediate lever. The improved lock lever simplifies the door latch device.
Furthermore, it is another object of the present invention to provide a door latch device having a lock lever and an open link arranged on the interior side of the latch device, where it is difficult to be illegally accessed from the outside.
Furthermore, it is another object of the present invention to provide a door latch device, in which a lock lever and an open link to be displaced by power of a motor are contained in a housing for shutting off an illegal access from the outside.
Furthermore, it is another object of the present invention to provide a door latch device capable of well absorbing the external force which concentrically acts on the engaged part of the latch and the striker because of a vehicle accident or the like.
Furthermore, it is another object of the present invention to provide a door latch device having a striker guide which is small and light, and can be manufactured at a low cost.